adding grass to a scene
Finished Result :



You will need to use a particle system :


Be sure that the origin point of the objects (that will be placed) is down.
Then select your objects and press Ctrl +
G
Select your plane where the grass objects will be placed, and in properties panel click on particle system and click plus
Continue From here in images :






Be sure to put a check-mark beside advance :





Finished :


If you want decrease the number of objects just decrease the number.